linux-kernel - Re: [PATCH v4 06/10] PCI: Add PCIe Device 3 Extended Capability enumeration

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Message-ID: <20250729162310.00001fbb@huawei.com>
Date: Tue, 29 Jul 2025 16:23:10 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Dan Williams <dan.j.williams@...el.com>
CC: <linux-coco@...ts.linux.dev>, <linux-pci@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bhelgaas@...gle.com>, <aik@....com>,
	<lukas@...ner.de>, Ilpo Järvinen
	<ilpo.jarvinen@...ux.intel.com>, Samuel Ortiz <sameo@...osinc.com>, "Xu
 Yilun" <yilun.xu@...ux.intel.com>
Subject: Re: [PATCH v4 06/10] PCI: Add PCIe Device 3 Extended Capability
 enumeration

On Thu, 17 Jul 2025 11:33:54 -0700
Dan Williams <dan.j.williams@...el.com> wrote:

> PCIe 6.2 Section 7.7.9 Device 3 Extended Capability Structure,
> enumerates new link capabilities and status added for Gen 6 devices. One
> of the link details enumerated in that register block is the "Segment
> Captured" status in the Device Status 3 register. That status is
> relevant for enabling IDE (Integrity & Data Encryption) whereby
> Selective IDE streams can be limited to a given Requester ID range
> within a given segment.
> 
> If a device has captured its Segment value then it knows that PCIe Flit
> Mode is enabled via all links in the path that a configuration write
> traversed. IDE establishment requires that "Segment Base" in
> IDE RID Association Register 2 (PCIe 6.2 Section 7.9.26.5.4.2) be
> programmed if the RID association mechanism is in effect.
> 
> When / if IDE + Flit Mode capable devices arrive, the PCI core needs to
> setup the segment base when using the RID association facility, but no
> known deployments today depend on this.
> 
> Cc: Lukas Wunner <lukas@...ner.de>
> Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Samuel Ortiz <sameo@...osinc.com>
> Cc: Alexey Kardashevskiy <aik@....com>
> Cc: Xu Yilun <yilun.xu@...ux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>


> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 1b991a88c19c..2d49a4786a9f 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -751,6 +751,7 @@
>  #define PCI_EXT_CAP_ID_NPEM	0x29	/* Native PCIe Enclosure Management */
>  #define PCI_EXT_CAP_ID_PL_32GT  0x2A    /* Physical Layer 32.0 GT/s */
>  #define PCI_EXT_CAP_ID_DOE	0x2E	/* Data Object Exchange */
> +#define PCI_EXT_CAP_ID_DEV3	0x2F	/* Device 3 Capability/Control/Status */
>  #define PCI_EXT_CAP_ID_IDE	0x30    /* Integrity and Data Encryption */
>  #define PCI_EXT_CAP_ID_PL_64GT	0x31	/* Physical Layer 64.0 GT/s */
>  #define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_PL_64GT
> @@ -1227,6 +1228,12 @@
>  /* Deprecated old name, replaced with PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE */
>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE
>  
> +/* Device 3 Extended Capability */
> +#define PCI_DEV3_CAP		0x4	/* Device 3 Capabilities Register */

Similar to earlier cases I'd make these 0x04 etc just to copy local style + match spec.


> +#define PCI_DEV3_CTL		0x8	/* Device 3 Control Register */
> +#define PCI_DEV3_STA		0xc	/* Device 3 Status Register */
> +#define  PCI_DEV3_STA_SEGMENT	0x8	/* Segment Captured (end-to-end flit-mode detected) */
> +
>  /* Compute Express Link (CXL r3.1, sec 8.1.5) */
>  #define PCI_DVSEC_CXL_PORT				3
>  #define PCI_DVSEC_CXL_PORT_CTL				0x0c